Baseline White Matter Neuroinflammation Predicts Cognitive Decline in Alzheimer Disease

Abstract

AbstractBackgroundNeuroinflammation, an intrinsic immune response of the nervous system, is important in an early phase of Alzheimer Disease (AD) pathogenesis. However, it is largely unclear how neuroinflammation promotes the clinical progression of AD. Extracellular water edema (ECW) from Neuro‐inflammation imaging (NII), a diffusion‐based MRI approach for neuroinflammation, has been utilized to asses white matter (WM) neuroinflammation in AD. This study aims to investigate the relationship between WM neuroinflammation and longitudinal cognitive changes in AD.MethodThis study included 286 participants who were enrolled in ongoing research at the Knight ADRC at Washington University in Saint Louis. The CSF levels of Aβ42/Aβ40 and ptau181 measured with the automated Lumipulse platform were used to categorize the participants as being positive or negative amyloid (A) and tau (T), respectively (Table 1). As measures of cognitive performance, the Knight ADRC Preclinical Alzheimer Cognitive Composite (Knight ADRC‐PACC) and a Global composite score were employed for each individual. The rates of change of cognitive measures were calculated for each individual. The NII was acquired with a multi‐b value scheme (bmax =1400s/mm2 and 25 directions). The total WM neuroinflammation (NII‐ECW) was obtained using the TBSS (http://www.fmrib.ox.ac.uk/fsl) based WM skeleton. Randomise in FSL was utilized to examine voxel‐wise relationships between NII‐ECW and the rate of change of cognitive measures. Non‐parametric Kruskal‐Wallis and Chi‐square tests were employed for comparing continuous and categorical variables of the participants’ demographics, respectively. The group differences of NII‐ECW were tested using one‐way ANOVA. All statistical tests were conducted in R (R Core Team, 2020). Age, sex, and APOE ε4 carrier status were adjusted as covariates.Result Table 1 summarizes demographic data. When compared to the A‐T‐ group, the A+T+CDR0 and A+T+CDR0.5 groups had higher NII‐ECW (Figure 1). When the A+T+CDR1 group was compared to the other groups, there was no group difference in NII‐ECW. There were substantial negative associations between the NII‐ECW and the rates of change of cognitive measures in the widespread WM regions (Figure 2).ConclusionOur data suggest that neuroinflammation increases early in preclinical AD and decreases later in the disease. Furthermore, baseline neuroinflammation as measured by NII‐ECW predicts cognitive decline in AD.